Bank segment - Reconciliation of Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Condensed Income Statements, Captions [Line Items]
Gain on sale of investment securities, net	$ 528	$ 0
Revenues	642,946	677,186
Provision for credit losses	(8,435)	10,401
Less: Retirement defined benefits expense (credit)—other than service costs	(2,435)	934
Total expenses	544,915	617,484
Operating income - Bank	98,031	59,702
Income before income taxes	80,196	39,696
American Savings Bank (ASB)
Condensed Income Statements, Captions [Line Items]
Interest and dividend income	58,620	64,975
Total noninterest income	19,039	14,763
Gain on sale of investment securities, net	528	0
Revenues	77,131	79,738
Total interest expense	1,489	3,900
Provision for credit losses	(8,435)	10,401
Noninterest expense	47,503	46,468
Less: Retirement defined benefits expense (credit)—other than service costs	(1,278)	434
Total expenses	41,835	60,335
Operating income - Bank	35,296	19,403
Income before income taxes	$ 37,102	$ 18,969